SCHRIEVER AIR FORCE BASE, Colo. (AP) – The Air Force said it’s investigating how an airman managed to get his own handgun onto a sensitive air base in Colorado where he barricaded himself in a building for 10 hours before surrendering.

Nico Cruz Santos, 21, was taken into custody at Schriever Air Force Base at about 8 p.m. Monday, officials said. No injuries were reported.

The base about 60 miles south of Denver controls more than 60 military satellites, including those used for GPS. The Air Force said satellite operations weren’t disrupted.

Officials said Santos was in a building where personnel prepare for deployment. The satellite control rooms are in a separate, heavily guarded area.

Authorities said Santos faces a possible discharge for an unrelated crime in civilian court. Santos pleaded guilty in September to a charge of attempted sexual exploitation of a child in Gilpin County west of Denver. He faces up to 18 months in prison. Sentencing is Dec. 16.

Santos is being held in the Teller County jail in Divide, Colo., under an agreement between the county and the Air Force base.

Air Force officials have not said whether he will face prosecution in civilian or military court over the standoff. Personal weapons are forbidden on the base.

Santos is a member of the 50th Security Forces Squadron and has been in the Force for two years and 9 months, officials said.